The development in coastal areas requires engineering solutions to ecological and environmental problems such as seawater intrusion, stability of coastal engineering structures, beach dewatering for construction purposes, and deterioration of the marine environment. Although numerical solutions have become standard tools for analyzing such systems [Boufadel, 2000], analytical solutions are still needed because they can reveal the governing parameters of the system, and provide benchmarks for numerical solutions. Analytical studies for tide-induced groundwater flow are numerous. They can be divided into two classes based on aquifer complexity: single aquifer [e.g., Jacob, 1950; Drogue et al., 1984; Sun, 1997; Townley, 1995; Trefry, 1999; Li et al., 2000, 2002] and multilayered aquifer system [e.g., van der Kamp, 1973; Jiao and Tang, 1999; Li et al., 2001; Jeng et al., 2002; Li and Jiao, 2001a, 2001b, 2002a, 2002b, 2003].
 Groundwater flow in confined coastal aquifers that extend under the sea has been studied by van der Kamp , Li and Chen [1991a, 1991b], and Li and Jiao [2001a]. In these studies the boundary condition used was that the subcrop of the aquifer extending under the sea is open on the sea side, and thus directly connected to the sea hydraulically. This condition is not typical, because there is usually a layer of sediment on the sea floor that separates the confined aquifer from the sea [Li and Chen, 1991b]. Such a layer can be modeled as a leaky boundary condition for the groundwater flow in the confined aquifer. Interestingly, such a realistic conceptualization has not been addressed in the literature, and many observed tide-induced groundwater level fluctuations could not be reasonably explained by the existing analytical or even numerical simulations. An example is in the work of Cheng et al. , where they could not explain the fluctuations in piezometer GK2A in the Jahe River Basin, Shandong Province, China that was located about 200 m inland from the coastline in a deep confined coastal aquifer. While the analytical solutions and numerical study predictive considerable time lag, observations indicated no delay in the response.
 The objective of this paper is to develop a solution for the tide-induced groundwater head fluctuations in a confined coastal aquifer, whose subcrop under the sea is covered with a layer of sediment. The validity of the solution is examined by comparison to field observations from the piezometer GK2A.